Assad regime and opposition demand international inquiry to look into alleged chemical attack near Aleppo city.

Syria's government and rebels have demanded an international inquiry into a deadly attack which both sides cite as an evidence that the other has used chemical weapons.

Bashar Jaafari, Syria's UN ambassador, announced on Wednesday that he had asked the UN to "form a specialised, independent and neutral technical mission" to investigate the use of chemical weapons by the opposition in the attack in the town of Khan al-Assal near northern city of Aleppo.

The attack, which killed 26 people on Tuesday, if confirmed, would be the first use of chemical weapons in the nearly two-year-old conflict.

"The Syrian government, if it has such weapons, will never use it against its own population," Jaafari said.

Denying any involvement into the incident, the rebels have accused the government forces of using the chemical weapons. They have also called for an inquiry into the deadly attack.

The UN, however, said on Wednesday that Syrian government had made no formal request for the investigation into the government claims that opposition rebels had used chemical weapons.

'Crime against humanity'

Martin Nesirky, the UN spokesman, appeared to counter a statement by Jaafari that Syria had asked for the "independent" inquiry into the claims.

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"I think we will have something further to say once we have received a formal request which we have so far not received," Nesirky told reporters.

"The secretary general remains convinced that the use of chemical weapons by any party under any circumstances would constitute an outrageous crime," the UN spokesperson said.

The opposition Syrian National Coalition said it wanted an "international investigation into the alleged chemical attacks" in Khan al-Assal as well as Otaiba, a town near the capital city of Damascus.

"The Coalition would like all parties and individuals involved in this reprehensible crime to be brought to justice," it said in a statement.

"Testimonies and images from the attacks [on Tuesday] demonstrate that these banned weapons have been used, in what amounts to a crime against humanity," it added.

UN Security Council nations are remaining cautious about the claims.

"We simply don't have any information to corroborate, verify, substantiate the allegations by either side," a senior UN diplomat has said.

'Red line'

Washington has disputed the regime's claim and said there was no evidence that the rebels had fired chemical weapons.

"So far we have no evidence to substantiate the reports that chemical weapons were used [on Tuesday]," said Robert Ford, the US ambassador to Syria, adding that the administration was extremely concerned and trying to verify reports of such weapons being used.

Barack Obama, the US president, has previously stated that the use, deployment or transfer of chemical weapons to be his "red line" for possible military intervention in Syria.

Britain said that the reports of the chemical attack strengthened the case for relaxing a European Union arms embargo on the country.

France and the UK have been pushing for the EU ban to be eased to allow the flow of arms to outgunned rebels, a move opposed by several EU countries and Russia.